Typically, a Personal Area Network (PAN) is a small-sized network, the size of which is smaller than that of a LAN, and is generally indicative of intercommunication between information communication devices located in a personal area having a predetermined diameter of about 10 m. If a wireless communication scheme is applied to the above-mentioned PAN, a Wireless Personal Area Network (WPAN) is provided. The IEEE 802.15 Working Group is indicative of a short-distance wireless network standard, and prescribes the following four task groups under the WPAN. The four task groups are composed of the IEEE 802.15.1 standard indicative of a Bluetooth standard, the IEEE 802.15.3 standard, the IEEE 802.15.3a standard, and the IEEE 802.15.4 indicative of ZigBee. In this case, the IEEE 802.15.3 standard and the IEEE 802.15.3a standard relate to a high Rate WPAN.
The Bluetooth standard employs an Industrial, Scientific, and Medical (ISM) band of 2.4 GHz, performs networking via multiple access among a plurality of Bluetooth devices, and provides performance of a communication distance of 10 m and a communication speed of 1 Mbps. Therefore, a mobile phone hands-free apparatus based on the above-mentioned Bluetooth standard has already been made commercially available and placed on the market. If a user employs the above-mentioned mobile phone hands-free apparatus based on the Bluetooth standard, the user can conveniently make a phone call with a desired called party even when the user has difficulty in using a mobile phone, for example, when the user drives a vehicle or performs a specific task. Also, if the user employs the above-mentioned mobile phone hands-free apparatus the user can conveniently make a phone call with a desired called party even when the user puts the mobile phone in a bag, a handbag, or a pouch, etc. However, the above-mentioned Bluetooth scheme has been prescribed to perform a variety of complicated functions, such that it causes complicated signal processing and hardware configuration, and increases power consumption, resulting in an increased rate of replacement of a mobile phone battery.